A number of high-precision measurement systems may be useful in materials processing. These high-precision measurement systems may include, but are not limited to, mass flow controllers (MFCs) and mass flow meters (MFMs).
It may be desirable and sometimes necessary to test, or verify, the accuracy of an MFC or an MFM. One way to verify the accuracy of an MFC or MFM is through a rate-of-rise (ROR) flow verifier. A typical ROR flow verifier may include a volume, a pressure transducer, and two isolation valves, one upstream and one downstream. The valves may be closed during idle, and may open when a run is initiated, allowing flow of fluid from the MFC (or MFM) through the flow verifier. Once fluid flow has stabilized, the downstream valve may be closed, and as a result the pressure may begin to rise in the volume. The pressure transducer may measure the pressure rise. This measurement may be used to calculate the flow rate, thereby verifying the performance of the ROR flow verifier.
Sometimes, measurement errors may result from connecting volumes in the flow path between the MFC and the ROR flow verifier, such as external plumbing located upstream from the ROR flow verifier. As fluid from the MFC (or MFM) flows from the MFC along the flow path through the plumbing or other type of connecting volume, the resulting pressure drop may cause inaccuracies in the pressure measurements by the pressure transducer.
For these reasons, there is a need for a system and method that can effectively prevent plumbing or other elements located upstream of the mass flow verifier from affecting the accuracy of the flow verification process.